1. Field of the Invention
The present invention involves medical devices that are capable of providing intravascular radiation therapy.
2. Description of the Related Art
Percutaneous transluminal coronary angioplasty (PTCA) is a medical procedure used to open arteries that have been partially closed (xe2x80x9cstenosedxe2x80x9d) by the buildup of atherosclerotic plaque or other materials, and accordingly pass a reduced amount of blood. In a typical PTCA procedure, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries. The guiding catheter is advanced therein until the distal tip is in the ostium of the desired coronary artery. A guide wire and dilation catheter having an inflatable balloon on the distal end thereof are introduced through the guiding catheter with the guide wire slidably disposed within an inner lumen of the dilation catheter. The guide wire is first advanced out of the distal end of the guiding catheter and is then maneuvered into the patient""s coronary vasculature containing the lesion to be dilated, and is then advanced beyond the lesion. Thereafter, the dilation catheter is advanced over the guide wire until the dilation balloon is located across the lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress against the atherosclerotic plaque of the lesion for remodeling the vessel. The balloon is then deflated so that the dilation catheter can be removed and blood flow resumed through the dilated artery.
After an angioplasty procedure, restenosis at or near the site of the original stenosis in the artery occasionally occurs. The smooth muscle cells of the artery may proliferate at the site of angioplasty treatment. Restenosis may result in a reformation of the lesion and a narrowing of the artery at the site.
Various devices and methods for the prevention of restenosis have been developed, including the use of an expandable stent on the distal end of the catheter designed for long-term implantation in the body lumen. Other devices and methods for the prevention of restenosis after angioplasty or another arterial intervention procedure employ a radiation source delivered through a balloon. The radiation operates to destroy the proliferating cells, thereby preventing development of restenosis. A medical device and method for such a radiation therapy is described in U.S. Pat. No. 5,910,101, which is incorporated herein by reference in its entirety.
An undesirable effect of radiation therapy, however, is that endothelial cells of the vessel at the treatment site are destroyed. Moreover, re-endothelialization, which is the re-growth of endothelial cells from neighboring areas over the area provided with radiation therapy, does not readily occur. Recent research has shown that endothelial cells perform various functions that help to maintain the health of a blood vessel, including producing nitric oxide, and regulating the concentration of pro-thrombotic and anti-thrombotic materials in the bloodstream. Absent sufficient re-endothelialization, conditions such as acute thrombosis, platelet aggregation at the site of radiation, and acute closure of the vessel, can occur. As a result of these conditions, the time required for the vessel to heal is increased.
To address such conditions, patients who undergo PTCA and radiation therapy receive an antiplatelet drug, such as heparin, by systemic administration for a period of two to three months after the PTCA procedure. However, there are drawbacks to such systemic therapy. For example, patients sometimes fail to comply with a prescribed systemic drug therapy regime for such a long period of time. Moreover, since the heparin or other antiplatelet drug is administered systemically, rather than locally, high dosages must be provided to yield a therapeutic effect. Such high dosages can result in undesirable complications in the patient, such as internal bleeding, and aneurysms.
Thus, there is a need for an improved method of providing intravascular radiation therapy after a PTCA procedure or other interventional procedure that reduces the risk of delayed reendothelialization, combats restenosis, advances the goals of the PCTA or other interventional procedure, and/or otherwise promotes the health of the vessel and surrounding tissue.
The present invention provides methods and structures for locally delivering a simultaneous radiation treatment and drug treatment to an intravascular treatment site. By providing both types of treatments simultaneously in one surgical procedure, common problems that can arise after, for example, PCTA procedures, such as restinosis and/or delayed reendotheliallization, can be addressed in a preventative manner.
In accordance with one embodiment of the present invention, a method for treating a vascular lumen and surrounding tissue is provided. The method includes locally delivering a therapeutic substance to a treatment site in a vascular lumen contemporaneous with locally delivering a radiation treatment to the treatment site. For example, the delivery of the therapeutic substance may be simultaneous with the radiation treatment. The therapeutic substance may be an antiplatelet substance, an antithrombotic substance, a thrombolytic substance, or a mixture thereof, among other possibilities.
In accordance with one embodiment the present invention, the simultaneous radiation and therapeutic substance treatments are locally delivered to the treatment site by an intravascular catheter assembly. The catheter assembly includes a catheter body having a first end adapted to remain external to a patient""s body, an opposite second end including a porous inflation region adapted to be positioned at the treatment site, a first lumen and a second lumen. The inflation region is adapted to inflate against a portion of a vascular wall, and to center the second lumen along a central axis of the vascular lumen at the treatment site. The inflation region is further adapted to deliver the therapeutic substance to the treatment site through pores in the inflation region. A radiation source is deliverable through the second lumen of the catheter body so as to provide the radiation treatment.
In accordance with another embodiment the present invention, a stent is implanted at the treatment site during the same surgical procedure as the simultaneous radiation and therapeutic substance treatments. One embodiment of an intravascular catheter assembly for performing such a procedure includes an inflation region including a substantially impermeable internal balloon, a permeable external balloon over the internal balloon, and a crimped stent wrapped over the external balloon. As above, the body of the catheter includes internal lumens, including lumens for inflating the internal and external balloons, and a central lumen through which the radiation source is delivered to the treatment site. Inflation of the inflation region results in deployment of the stent, centering of the central lumen in the vascular lumen, and delivery of the therapeutic substance through pores of the inflation region to the treatment site. The stent supports the vascular wall after completion of the procedure.